Generally, an internal combustion engine is an apparatus for generating power by burning fuel mixed with intake air in a combustion chamber. In an internal combustion engine, a small amount of gas (which is called blow-by gas) leaks from a combustion chamber into a crankcase. Because the blow-by gas is a factor for air pollution, the blow-by gas is controlled to return to the combustion chamber for re-burning.
A system provided to an engine for such re-burning of the blow-by gas is generally called a positive crankcase ventilation (PCV) system, and a system for supplying intake air to a cylinder is called an air intake system. In a typical PCV system, the blow-by gas is supplied first to a cylinder head from the crankcase through a passage formed in the cylinder block.
Subsequently, the blow-by gas is supplied to an intake manifold from the cylinder head consecutively through a PCV valve of the PCV system, a PCV hose, and a PCV nipple. Then the blow-by gas is supplied to the combustion chamber from the intake manifold through intake runners.
But, because water vapor is usually present in the blow-by gas, the vapor condenses into water, so water may freeze in the PCV nipple or the PCV valve of the PCV system after being gathered there. To prevent freezing in a PCV nipple or a PCV valve, the PCV nipple connected to a PCV hose may be mounted to an intake runner of an intake manifold. When the PCV hose is connected to the intake runner, the freezing in the PCV nipple can be prevented by the heat produced from the engine.
But in this system, because the blow-by gas from the PCV nipple is supplied only to a specific combustion chamber through a specific intake runner, the supply of the blow-by gas becomes biased to the specific cylinder, resulting in non-uniform supply of the blow-by gas to the combustion chambers.
The information disclosed in this section is only for enhanced understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.